Handbook of Information Security Management
(Publisher: CRC Press LLC)
Author(s): Hal Tipton and Micki Krause, Consulting Editors
ISBN: 0849399475
Publication Date: 01/01/98

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User Validation Protection

The protection strategy should reflect the types of portable computing to be supported. If remote access to the company’s host computers and networks is part of the portable computing capabilities, then strict attention should be paid to implementing a high-level remote access validation architecture. This may include use of random password generation devices, challenge/response authentication techniques, time-synchronized password generation, and biometric user identification methods. Challenge/response authentication relies on the user carrying some form of token that contains a simple encryption algorithm; the user would be required to enter a personal ID to activate it. Remote access users are registered with a specific device; when accessing the system, they are sent a random challenge number. Users must decrypt this challenge using the token’s algorithm and provide the proper response back to the host system to prove their identity. In this manner, each challenge is different and thus each response is unique. Although this type of validation is keystroke-intensive for users, it is generally more secure than one-time password methods; the PIN is entered only into the remote users’ device, and it is not transmitted across the remote link.

Another one-time password method is the time-synchronized password. Remote users are given a token device resembling a calculator that displays an eight-digit numeric password. This device is programmed with an algorithm that changes the password every 60 seconds, with a similar algorithm running at the host computer. Whenever remote users access the central host, they merely provide the current password followed by their personal ID and access is granted. This method minimizes the number of keystrokes that must be entered, but the personal ID is transmitted across the remote link to the host computer, which can create a security exposure.

A third type of high-level validation is biometric identification, such as thumb print scanning on a hardware device at the remote user site, voice verification, and keyboard dynamics, in which the keystroke timing is figured into the algorithm for unique identification. The portable computer user validation from off-site should operate in conjunction with the network security firewall implementation. (A firewall is the logical separation between the company-owned and managed computers and public systems.) Remote users accessing central computing systems are required to cross the firewall after authenticating themselves in the approved manner. Most first-generation firewalls use router-based access control lists (ACLs) as a protection mechanism, but new versions of firewalls may use gateway hosts to provide detailed packet filtering and even authentication.

Data Disclosure Protection

If standalone computers are used in a portable or mobile mode outside of the company facility, consideration should be given to requiring some form of password user identification on the individual unit itself. Various software products can be used to provide workstation-level security.

The minimum requirements should include unique user ID and one-way password encryption so that no cleartext passwords are stored on the unit itself. On company-owned portables, there should be an administrative ID on all systems for central administration as necessary when the units return on-site. This can help ensure that only authorized personnel are using the portable system. Although workstation-based user authentication isn’t as strong as host-based user authentication, it does provide a reasonable level of security. At the least, use of a commercial ID and password software products on all portables requires that all users register for access to the portable and the data contained on it.

Other techniques for controlling access to portables include physical security devices on portable computers. Though somewhat cumbersome, these can be quite effective. Physical security locks for portables are a common option. One workstation security software product includes a physical disk lock that inserts into the diskette drive and locks to prevent disk boot-ups that might attempt to override hard-disk-resident software protections.

In addition to user validation issues (either to the host site or the portable system itself), the threat of unauthorized data disclosure must also be addressed. In the remote access arena, the threats are greater because of the various transmission methods used: dial-up over the public switched telephone network, remote network access over such media as the Internet, or even microwave transmission. In all of these cases, the potential for unauthorized interception of transmitted data is real. Documented cases of data capture on the Internet are becoming more common. In the dial-up world, there haven’t been as many reported cases of unauthorized data capture, though the threat still exists (e.g., with the use of free-space transmission of data signals over long-haul links).

In nearly all cases, the most comprehensive security mechanism to protect against data disclosure in these environments is full-session transmission encryption or file-level encryption. Simple Data Encryption Standard (DES) encryption programs are available in software applications or as standalone software. Other public domain encryption software such as Pretty Good Privacy (PGP) is available, as are stronger encryption methods using proprietary algorithms. The decision to use encryption depends on the amount of risk of data disclosure the company is willing to accept based on the data types allowed to be processed by portable computer users.

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